Noise produced by gas turbine engines is largely caused by pressure and acoustic vibrations which can occur in and around the combustion chamber under certain conditions. Many advancements have been made to reduce the overall noise levels generated by gas turbine engines. However, few have enabled the reduction of noise generated by the combustion chamber of such a gas turbine engine.
In some cases, the noise of the combustion chamber is damped by providing Helmholtz resonators as damping elements to eliminate undesirable vibrations, which contribute to noise levels. However, combustors incorporating Helmholtz resonators are generally complex to manufacture.
In other cases, the combustors have a double wall construction, i.e. interconnected inner walls defining the combustion chamber surrounded by interconnected outer walls to define an annular free space therebetween. The outer walls have impingement holes defined therein which permit compressed air from around the combustion chamber to pass through to impinge on the inner walls. The inner walls have effusion holes defined therein to permit the air to effuse into the combustion chamber. However such a design generally permits the reduction of only a specific range of noise frequencies. In addition, the double wall construction generally renders the combustor more complex and costly to manufacture.
Accordingly, improvements are desirable.